1. Field of the Invention
The invention relates to sports and medicine, particularly to applications in which the capacity of a person is controlled during a fitness exercise according to a value of respiratory flow measured before the fitness exercise.
During a fitness exercise the ventilation frequency, i.e. inspiration and expiration, increases as the workload increases. Normally the respiratory capacity of a person is always so good that is does not limit the fitness exercise even at heavy workload, but the oxygen uptake and removal of carbon dioxide are sufficient for metabolism. The respiratory capacity may, however, limit exercising if the person suffers from a disease of respiratory organs or respiratory bronchioles, such as asthma. Persons suffering from exercise induced asthma may experience dyspnoea and stridor during a fitness exercise because due to asthma their respiratory organs may be inflamed and swollen. The number of asthmatics is increasing in the West, being already about 2 to 4% of the population.
2. Description of the Prior Art
The basis for treating asthma and other respiratory diseases is good physical condition which prevents serious complications and helps to cope with difficult situations. The general instructions for improving the physical condition cannot be applied to asthmatics because their respiratory flow values vary considerably. In practice, asthmatics therefore have to determine their respiratory flow before each fitness exercise and decide on the exercise workload on the basis of the respiratory flow. U.S. publication No. 5,626,144 discloses a PEF meter (Peak Expiratory Flow) for measuring the respiratory flow. By blowing into the meter the user finds out the current expiratory flow. On the basis of the measured value the person can decide whether to take medication before a fitness exercise and plan the exercise workload at a broad level. U.S. publication No. 3,675,640 describes a solution between a variable describing the person""s capacity, such as inhaled oxygen or exhaled carbon dioxide, and physical stress. In the solution described in the publication the patient""s maximal capacity is determined according to measurement results obtained during a fitness exercise in a clinical environment and results achieved by a healthy person.
The prior art method of determining the capacity is designed for hospitals and requires a complex and expensive apparatus. Consequently, the method cannot be applied in everyday sports.
The object of the invention is to provide an improved method and an apparatus implementing the method for determining the stress level of a fitness exercise. This is achieved with the following method of controlling a fitness exercise performed by a person. The method comprises measuring the person""s heart rate information during the fitness exercise and informing the person if, during the fitness exercise, the value of a stress parameter formed from the measured heart rate information exceeds a threshold value formed for the stress parameter before the fitness exercise. In the method the threshold value of the stress parameter is formed for the fitness exercise using the value of the person""s expiratory flow.
The invention also relates to a heart rate monitor which comprises means for measuring the heart rate of a person during a fitness exercise, a calculation unit for forming the value of one or more stress parameters from the measured heart rate during the fitness exercise, the calculation unit being arranged to compare the value of the stress parameter during the fitness exercise with a threshold value formed for the stress parameter before the fitness exercise, the heart rate monitor further comprising display means for showing exceeding of the threshold value of the stress parameter to the person during the fitness exercise. The calculation unit is arranged to use the value of the person""s expiratory flow measured for the fitness exercise for forming the threshold value of the stress parameter.
The invention relates to a method and an apparatus for determining the optimal exercise level of a person and for controlling it during a fitness exercise. The solution is particularly suitable for a fitness exercise performed by a person who suffers from a disease of respiratory organs, such as asthma. In this description a fitness exercise refers to a physical exercise performed at a heart rate level of at least about 20 heart beats per minute over the person""s heart rate at rest.
A method according to a preferred embodiment of the invention comprises measuring the heart rate information of a person during a fitness exercise. The heart rate information to be measured refers to heart rate parameters that can be measured from heartbeats, such as the average heart rate per minute, standard deviation of the heart rate, change rate of the heart rate or other similar parameters that can be calculated from the heart rate. One or more of the above-mentioned heart rate parameters are used as a stress parameter which describes the exercise workload. A threshold value which should not be exceeded during the fitness exercise is set for the stress parameters. In an embodiment the person""s stress level during the fitness exercise is used as the stress parameter in addition to a heart rate parameter or instead of it. The stress level is formed using one or more of the following parameters: one or more heart rate parameters, one or more physiological parameters which describe the person""s physiological properties, one or more stress parameters which describe the exercise workload.
The threshold value of the stress parameter is formed before the fitness exercise, and preferably the threshold value is re-formed before each fitness exercise The person""s current maximal expiratory flow is used for forming the threshold value. In a preferred embodiment the expiratory flow is measured with a PEF meter. In an embodiment the measured PEF value is compared with the reference value of expiratory flow, and the threshold value of the stress parameter is formed on the basis of this comparison. The reference value of expiratory flow means e.g. the person""s maximum value of expiratory flow. The reference value can also be formed on the basis of tabulated information or by means of a neural network using one or more physiological parameters. The method according to the invention is preferably implemented by a heart rate monitor into which the PEF value measured by the user is fed before the fitness exercise. In an embodiment the heart rate monitor forms the reference value of expiratory flow, which is read from a table included in the heart rate monitor or formed by means of a neural network using the physiological parameters to be fed into the heart rate monitor. During the fitness exercise the heart rate monitor measures the heart rate, and in an embodiment one or more of the following items are presented on the display of the heart rate monitor: heart rate parameter, threshold value of the heart rate parameter, stress level, threshold value of the stress level. Furthermore, if the user exceeds the threshold value of the stress parameter during the fitness exercise, the heart rate monitor gives a sound signal or a voice message, informs the user of exceeding by displaying information on the display of the heart rate monitor or with touch information, such as vibration or the like, in which case the user can reduce the exercise workload or finish the exercise.
In an embodiment of the invention the apparatus implementing the method according to the invention is a heart rate monitor. The heart rate monitor is a device employed in sports, which measures human heart rate information from an electrical impulse transmitted by the heart, from the pressure produced by the heart beat on an artery or optically from the blood movement in an artery. The structures of the heart rate monitors available vary. There are, for example, heart rate monitors which comprise an electrode belt to be fitted around the user"" chest and a wrist-worn receiver unit. The electrode belt measures the heart rate and transmits information on it to the receiver unit, which calculates heart rate parameters on the basis of the information received. Often, the receiver unit, i.e. the wrist monitor, also comprises a display for showing the heart rate information and other heart rate parameters formed in the heart rate monitor to the exerciser. In the present invention, information on the stress level during exercise and/or the threshold value corresponding to it are preferably shown on the display. The heart rate monitor can also be a one-piece device in which the measurement, processing and display are located in the electrode belt to be fitted around the chest, and thus there is no need to transmit the information to a separate receiver unit. Further, the structure of the heart rate monitor can be such that it only comprises a wrist-worn monitor which operates without the electrode belt to be fitted around the chest, measuring the heart rate from the vessel pressure or optically.
The heart rate monitor preferably also comprises means for feeding the measured value and the reference value of expiratory flow, user-specific physiological information and information on the exercise workload. The feeding means can be, for instance, a keypad of the heart rate monitor, display equipment that supports feeding of information, a speech controller, an optical feeding device, a telecommunications port for external control or the like.
The functions required by the method of the invention, such as calculation operations, a neural network or the like, are preferably implemented by software for a general-purpose processor. The functions can also be implemented as ASIC, with separate logic components or in a corresponding manner.
An advantage of the invention is that it provides an improved method of determining the optimal level for a fitness exercise to be performed by a person who suffers from a disease of respiratory organs before the fitness exercise. A further advantage of the invention is that it enables monitoring during the fitness exercise that the exercise workload remains at a suitable level for the person in question.